Cenozoic climate gradients in Eurasia — a palaeo-perspective on future climate change?

Recent studies in the frame of the NECLIME (Neogene Climate Evolution in Eurasia) network provide a comprehensive inventory of continental palaeoclimate data for various time slices reconstructed from the palaeobotanical record. The integrative analysis of spatial gradients and patterns observed from the proxy data, together with data obtained from numeric modelling studies considerably improved our knowledge about the functioning of the climate system in the Cenozoic. When compared to the present an overall warmer, more humid climate existed. Cenozoic climates are characterized by warm high latitudes, shallow latitudinal and longitudinal gradients and wet continental interiors while concentration of greenhouse gases was about at the present-day level or considerably higher. Thus, these past climates potentially are valuable to better understand future climate change because they allow empirical access to climate situations that do not or not yet exist today. In the present study, continental climate data calculated from micro- and macrofloras using the Coexistence Approach are analysed in order to compare past gradients and patterns and their anomalies relative to present-day conditions with future climate change scenarios. For the case study, three time intervals are selected: The Mid-Eocene represents a very warm period of the Cenozoic exemplifying greenhouse conditions with high atmospheric CO 2 of over 1.100 ppmv. The Mid-Miocene is known as outstanding warm time interval as well. The concentration of greenhouse gases is still controversially discussed, but was certainly below the Eocene level. A third interval selected, the Tortonian, represents a time-span of subsequent cooling with the beginning of Arctic glaciation. For this period, a pre-industrial CO 2 level is assumed. It is shown that the study of past climate patterns provides important clues when evaluating modelling results for future scenarios. Anomalies predicted under global warming partly coincide with the palaeoclimate data sets. As an example for greenhouse conditions, the Mid-Eocene data also show a strong warming of the high latitudes and a significant positive anomaly of winter temperatures in the continental interior as in the model study for the future scenario. However, for the Tortonian where a pre-industrial CO 2 can be assumed data show the best agreement with predicted patterns.